"We don't support, as a Government and as a Coalition, further lock-ups of our forests. We just don't support it," Mr Abbott said.

"We have quite enough national parks. We have quite enough locked up forests already. In fact, in an important respect, we have too much locked up forest.

"Why should we lock up as some sort of World Heritage sanctuary country that has been logged, degraded or planted for timber?

"Getting that 74,000 hectares out of World Heritage Listing, it's still going to leave half of Tasmania protected forever, but that will be an important sign to you, to Tasmanians, to the world, that we support the timber industry."

Mr Abbott told the dinner that Tasmania's forest workers have a friend in Canberra.

"When I look out tonight at an audience of people who work with timber, who work in forests, I don't see people who are environmental vandals; I see people who are the ultimate conservationists," he said.

While appointments to the new Forestry Advisory Council are still being finalised, Institute of Foresters national director Rob De Fegely has been named as co-chair.

Greens condemn 'massive assault on the environment'

Greens leader Christine Milne says the Prime Minister's words send a clear message to the world "that Australia does not value its world heritage areas or its national parks".

"People are going to be pretty upset that Tony Abbott is mounting this massive assault on the environment," she said.

Any move to repeal the World Heritage classification on Tasmanian forests would ultimately prove destructive to the state's logging industry, she added.

"Tony Abbott has got it so wrong. The logging industry was on its knees in Tasmania because around the world nobody wants to buy timber products that come from old growth forest," she said.

"There's now a high level of recognition that we need to be protecting the last of our primary forests around the world."

Senator Milne said the recent peace deal with Tasmania's conservation movement had given loggers "some chance of a future in the plantations", but that Mr Abbott had threatened to "send Tasmania back to decades of conflict".

"What he'll actually do is destroy the forest industry, not to mention Tasmania's clean, green and clever brand which is our main asset and that comes from our World Heritage area," she said.

Warnings of return to conflict between environmentalists, industry

Tasmania's Deputy Premier, Bryan Green, says Mr Abbott's approach to the issue is a step backwards for the timber industry, and a return to the logging war between activists and timber workers.

He told ABC Local Radio the best way forward is through the treaty struck by environmentalists and the industry - the Tasmanian Forestry Agreement (TFA).

"We've taken massive steps forward in this industry as a result of the TFA, we're backing the TFA, we don't want to return to the trenches," he said.

"We want to continue to diversify the economy, we want to grow the forest industry based on the TFA as it's established."

The Wilderness Society's Vica Bayley says Mr Abbott's comments are an attack on the agreement's signatories.

"It's incredibly concerning because of the negative consequences this will have on Tasmania," he said.

"This will plunge Tasmania back into the heady conflicts of past year. This will have a massive negative impact on markets for Tasmanian timber products and put a black mark over Tasmania's brand as a clean green fantastic place."